Out of the photomechanical process in the field of printing duplication, the page make-up stage and the dot-to-dot working stage are improved in the operation efficiency and the operation environment by carrying out the operation under a brighter environment and a silver halide light-sensitive material for plate making capable of handling under such an environment as can be considered to be substantially as a bright room is provided.
A well known method for producing a light-sensitive material having low sensitivity to visible light and capable of handling in a bright room comprises the use of a silver halide emulsion mainly consisting of silver chloride and having added thereto an inorganic or organic desensitizer such as rhodium salt, iridium salt, pinakryptol yellow and phenosafranine. In a particularly preferred method, a rhodium salt and/or an organic desensitizer is used together with fine particle silver chloride or fine particle silver chlorobromide emulsion having a particle size of from 0.05 to 0.5 .mu.m and not subjected to chemical sensitization. Further, a method is also used where, in combination with the above-described emulsion, a yellow dye or an ultraviolet absorbing dye is incorporated into the light-sensitive material for the purpose of adjusting the sensitivity and imparting safety to the safe light.
On the other hand, the light-sensitive material for use in the page make-up stage or the dot-to-dot working stage is demanded to have a so-called superhigh contrast photographic properties such as high blacking density capable of clearly distinguishing the image area from the non-image area so as to provide good reproduction of a line image or a halftone image. In particular, when a halftone image and a line original are superposed on exposure (so-called superimposed letter image formation), the light-sensitive material is demanded to have a good reproduction property of a line image (letter image quality).
A known method for imparting a superhigh contrast photographic property to a light-sensitive material comprises the incorporation of a hydrazine derivative or a tetrazolium compound into the light-sensitive material, however, when this is used in combination with the above-described method where an inorganic or organic desensitizer, a yellow dye or an ultraviolet absorbing dye is incorporated into the light-sensitive material, there arise problems such that the high contrast effect given by the hydrazine derivative or the tetrazolium compound may be inhibited or the good reproduction property of a line image may be lost.
JP-A-60-140338 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-61-238049, JP-A-63-183438, JP-A-63-296034, JP-A-61-198147, JP-A-61-198148 and JP-A-61-240235 disclose an image system where a silver halide black-and-white photographic material for dot-to-dot working can have superhigh contrast photographic properties. However, the developer used in these publications has a pH of 11 or more.
The developer having a pH of 11 or more is susceptible to air oxidation and unstable and as a result, cannot endure a long-term storage. Accordingly, a system is demanded therefor where a silver halide photographic material containing a hydrazine derivative is developed with a developer having a lower pH to obtain a high contrast image.
However, if the pH of the developer is low, the high contrast effect due to the hydrazine derivative is reduced and a high contrast image cannot be obtained.
In order to achieve higher contrast, investigations on more active hydrazine derivatives and nucleation accelerators have been made, however, the photographic material is sometimes obliged to undergo reduction in the long-term storage stability.